You have to adjust them so that they are at the right height before you attach the backhoe. On mine, whent the remotes are active for the backhoe the 3pt doesn't move.
Also, be careful. Somehow I bent my antisway arms, I think it was caused by the backhoe. Don't really know how it happened. But, they were bent so bad that I had to replace them. Pull out the pins on the sway arms so that they free swing beforehand. And watch them carefully as you hook up the hoe.
Of course the degree of interference may be different depending on the backhoe. I have a Rhino 75.